This invention relates to detachable fasteners and more particularly to clasps used in jewelry pieces such as necklaces and bracelets.
The most widely used type of clasp for jewelry is the so-called "spring-ring" which is constituted by an openable ring made of two telescopic circular sections. The loop is resiliently kept closed by a coil spring coaxially mounted inside one of the circular sections. The operation of this clasp, as well as other types of commonly used clasps, requires a certain amount of dexterity. The thumbnail must be used to open the loop, a procedure extremely difficult for a female with long fingernails. The step of engaging the loop into an even smaller ring at the other end of the piece of jewelry requires not only good eyesight but also very steady hands, far beyond the abilities elderly persons. The main drawback of these types of clasps is that they require a two-hand operation which makes them extremely unpractical for bracelets.
The so-called "box clasp" was developed to aleviate some of the shortcomings of these earlier types of clasps. This latter design relies upon the spring action of one of the two end elements which is a strip of metal bent midway into a V shape then inserted into the box-like second element. The major drawback of this design is that the spring element quickly loses its resilience. Consequently, the "box clasp" cannot be relied upon to secure valuable jewelry pieces.